High-dose direct irradiation to a cardiac resynchronization therapy defibrillator infiltrated by metastatic thyroid papillary carcinoma in the sternum: A case report

Abstract

BackgroundBecause radiotherapy (RT) can cause malfunction of cardiovascular implantable electronic devices (CIEDs), patients with CIEDs who receive RT require careful management. A dose threshold of 2 Gy received by CIEDs has been largely adopted in several guidelines; thus, very few cases of direct exposure of CIEDs to RT have been reported. We report a case of a cardiac resynchronization therapy defibrillator (CRTD) directly exposed to high-dose RT in a patient with sternal metastasis of thyroid papillary carcinoma. Case reportThe patient was a 75-year-old man who was prescribed RT to control increasing sternal bone metastasis from thyroid papillary carcinoma. A CRTD device had been implanted for treatment of chronic heart failure and ventricular tachycardia, and the device was located adjacent to the 12.2 cm sternal bone metastasis. After careful consideration of the indications by the cancer board, including cardiologists, we decided to treat the metastasis, including the CRTD device, with RT. RT was performed using 10 MV X-rays at a total dose of 66 Gy in 22 fractions. The maximum and average doses of RT received by the CRTD were 68.3 and 64.7 Gy, respectively. Implantable cardioverter defibrillator function was turned off during RT, and device checks were performed every treatment session. No device malfunction had been detected until the patient died from heart failure at 15 months after treatment. Furthermore, neither tumor regrowth nor severe adverse events were observed. ConclusionFor patients with unavoidable exposure of a CIED to high-dose direct RT, careful risk assessment and appropriate safety management are important.